Risk factors of late-onset gestational diabetes diagnosed during 24-28 weeks of gestation after normal early screening: a case-control study.

Objective: To determine the risk factors associated with late-onset GDM (diagnosed between 24 and 28 weeks of gestation) after normal early screening.

Methods: A case-control study was conducted in 600 singleton pregnant women who started antenatal care before 20 weeks with normal early GDM screening. Repeat screening was performed at 24-28 weeks. Cases were 120 women with late-onset GDM and 480 controls were those without GDM. Risk factors for late-onset GDM were evaluated and pregnancy outcomes were compared.

Results: Cases were significantly older, and more likely to be overweight or obese. 50-g GCT of ≥ 160 mg/dL and abnormal 1 value of 100-g OGTT significantly increased the risk of late-onset GDM (p = 0.004 and < 0.001 respectively). Independent risk factors were abnormal 1 value of 100-g OGTT from first screening (adjusted OR 5.49, 95% CI 2.70-11.17, p < 0.001), age ≥ 30 years (adjusted OR 2.71, 95% CI 1.66-4.43, p < 0.001), DM in family (adjusted OR 1.76, 95% CI 1.07-2.88, p = 0.025), and BMI ≥ 25 kg/m (adjusted OR 1.86, 95% CI 1.17-2.97, p = 0.009). Late-onset GDM significantly increased the risk of preeclampsia, cesarean delivery, LGA, and macrosomia.

Conclusion: Independent factors associated with late-onset GDM included abnormal 1 value of 100-g OGTT from first screening, age ≥ 30 years, DM in family, and being overweight or obese.